Light-emitting display and method of manufacturing the same

ABSTRACT

A light-emitting display capable of maintaining low power consumption and improving display quality irrespective of the configuration of an auxiliary wiring. A second electrode and an auxiliary wiring are electrically connected to each other through a conductive contact section. Moreover, only a part of the auxiliary wiring is connected to the contact section. Even if the surface of the auxiliary wiring is oxidized, an increase in connection resistance is prevented. Moreover, a restriction on layout is not imposed at the time of forming the contact section.

RELATED APPLICATION DATA

This application is a division of U.S. patent application Ser. No.13/328,136 filed on Dec. 16, 2011, which is a continuation of U.S.patent application Ser. No. 12/304,094, filed Dec. 9, 2008, now issuedas U.S. Pat. No. 8,115,376 the entirety of which are incorporated hereinby reference to the extent permitted by law. U.S. patent applicationSer. No. 12/304,094 is the Section 371 National Stage ofPCT/JP2007/061511 filed on Jun. 7, 2007. This application claims thebenefit of priority to Japanese Patent Application Nos. 2006-168906,filed Jun. 19, 2006.

BACKGROUND

The present invention relates to a top emission system light-emittingdisplay and a method of manufacturing such a light-emitting display.

In recent years, as one of flat panel displays, organic EL displaysdisplaying an image through the use of an organic EL (ElectroLuminescence) phenomenon have received attention. The organic ELdisplays use the light-emitting phenomenon of an organic light-emittingdevice, so the organic EL displays have superior characteristics such asa wide viewing angle and low power consumption. Moreover, the organic ELdisplays have high responsivity to a high-definition high-speed videosignal, so the organic EL displays has been developed toward practicaluse specifically in a video field or the like.

As a drive system in the organic EL displays, an active matrix systemusing a thin film transistor (TFT) as a drive element is superior inresponsivity and resolution, compared to a passive matrix system, and inthe organic EL displays having the above-described characteristics, theactive matrix system is particularly considered as a suitable drivesystem. An active matrix type organic EL display includes a drive panelin which an organic EL element including an organic light-emitting layerand a drive element (the above-described thin film transistor) fordriving the organic EL display element are arranged, and has aconfiguration in which the drive panel and a sealing panel are bondedtogether by an adhesive layer so that the organic EL element issandwiched between the drive panel and the sealing panel. Moreover, theorganic EL element has a configuration in which the organiclight-emitting layer is formed between a pair of electrodes.

There are a bottom emission system organic EL display which emits lightfrom each organic EL element to the above-described drive panel side anda top emission system organic EL display which emits the light to theopposite direction, that is, the above-described sealing panel side;however, the latter is a mainstream of development, because the lattercan increase an aperture ratio.

Here, in the top emission system organic EL display, an electrode on alight extraction side, that is, on the sealing panel side is a commonelectrode for each organic EL element, and is made of, for example, alight-transmissive conductive material such as ITO (Indium Tin Oxide).However, such a light-transmissive conductive material has resistivity afew orders of magnitude higher than that in a typical metal material.Therefore, a voltage applied to the electrode on the light extractionside becomes nonuniform in a plane, so there is an issue that positionalvariations in light emission luminance among organic EL elements occur,and display quality declines.

Therefore, for example, Patent Document 1 discloses a technique in whichan auxiliary wiring for being connected to an electrode on a lightextraction side is formed of the same material as that of an electrodeon a drive panel side in the same layer as the electrode on the drivepanel side.

-   [Patent Document 1] Japanese Unexamined Patent Application    Publication No. 2002-318556

SUMMARY OF THE INVENTION

It is considered that when an auxiliary wiring is formed of a materialwith lower resistivity than that of an electrode on a light extractionside and is connected to the electrode on the light extraction side insuch a manner, the above-described in-plane nonuniformity of anelectrode voltage can be reduced to some extent.

However, in the above-described technique in Patent Document 1, in thecase where, for example, aluminum (Al) or an Al alloy is used for asurface of an electrode on a drive panel side, when the auxiliary wiringis formed of the same material as that of the electrode, the surface ofthe auxiliary wiring is easily oxidized. When the surface is oxidized,connection resistance between the auxiliary wiring and the electrode onthe light extraction side is increased to cause a large voltage drop inthis part. Therefore, the power consumption of a display is increaseddue to an increase in voltage drop.

Thus, in the conventional technique, it is difficult to prevent anincrease in power consumption irrespective of the configuration of theauxiliary wiring and improve display quality by achieving in-planeuniformity of an electrode voltage on the light extraction side.

In view of the foregoing, it is an object of the invention to provide alight-emitting display capable of maintaining low power consumption andimproving display quality irrespective of the configuration of anauxiliary wiring, and a method of manufacturing such a light-emittingdisplay.

A light-emitting display according to the invention including aplurality of drive elements, and a wiring section electrically connectedto the drive elements, the light-emitting display includes: a pluralityof first electrodes formed corresponding to the drive elements,respectively, on the drive elements and the wiring section; a pluralityof light emission sections formed on the first electrodes, respectively;a common second electrode formed of a material allowing light from thelight emission sections to pass therethrough, and arranged on theplurality of light emission sections; an auxiliary wiring section withlower resistance than that of the second electrode; and a conductivecontact section electrically connecting between the second electrode andthe auxiliary wiring section.

In the light-emitting display according to the invention, the secondelectrode and the auxiliary wiring are electrically connected to eachother through the conductive contact section, so even if the surface ofthe auxiliary wiring is oxidized, an increase in connection resistanceis prevented.

A method of manufacturing a light-emitting display according to theinvention includes: a step of forming a plurality of drive elements anda wiring section on a substrate, and electrically connecting between theplurality of drive elements and the wiring section; a step of forming afirst conductive layer on the drive elements and the wiring section; astep of forming a plurality of first electrodes corresponding to theplurality of drive elements, respectively, as well as an auxiliarywiring section by patterning the first conductive layer; a step offorming a light emission section on each of the first electrodes; a stepof forming a common second electrode of a material allowing light fromeach light emission section to pass therethrough on a plurality of thelight emission sections; and a step of forming a conductive contactsection, and electrically connecting between the second electrode andthe auxiliary wiring section through the contact section, wherein theauxiliary wiring section is formed of a material with lower resistancethan that of the second electrode.

In the light-emitting display and the method of manufacturing alight-emitting display according to the invention, it is preferable thatone conductive layer be formed, and the above-described wiring sectionand the contact section be formed by patterning the conductive layer. Inthe case where they are formed in such a manner, the wiring layer andthe contact section can be formed in the same step, so manufacturingsteps are simplified.

According to the light-emitting display or the method of manufacturing alight-emitting display of the invention, the second electrode and theauxiliary wiring are electrically connected to each other through theconductive contact section, so even if the surface of the auxiliarywiring is oxidized, an increase in connection resistance can beprevented. Therefore, irrespective of the configuration of the auxiliarywiring, low power consumption can be maintained, and display quality canbe improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing the configuration of a light-emittingdisplay according to a first embodiment of the invention.

FIG. 2 is a sectional view showing the configuration of thelight-emitting display shown in FIG. 1.

FIG. 3(A) and FIG. 3(B) are sectional views showing a part of main stepsof a method of manufacturing the light-emitting display shown in FIG. 1.

FIG. 4(A) and FIG. 4(B) are sectional views showing a step followingFIGS. 3(A) and (B).

FIG. 5(A) and FIG. 5(B) are sectional views showing a step followingFIGS. 4(A) and 4(B).

FIG. 6 is a sectional view showing the configuration of a light-emittingdisplay according to a comparative example.

FIG. 7 is a plot showing a relationship between a current flowingbetween electrodes and a voltage drop in an auxiliary wiring.

FIG. 8 is a sectional view showing the configuration of a light-emittingdisplay according to another comparative example.

FIG. 9 is a sectional view showing the configuration of a light-emittingdisplay according to a second embodiment.

FIG. 10(A) and FIG. 10(B) are sectional views showing a part of mainsteps of a method of manufacturing the light-emitting display shown inFIG. 9.

FIG. 11(A) and FIG. 11(B) are sectional views showing a step followingFIGS. 10(A) and (B).

FIG. 12(A) and FIG. 12(B) are sectional views showing a step followingFIGS. 11(A) and 11(B).

FIG. 13(A) and FIG. 13(B) are sectional views showing a step followingFIG. 12.

FIG. 14 is a sectional view showing the configuration of alight-emitting display according to a third embodiment.

FIG. 15(A) and FIG. 15(B) are sectional views showing a part of mainsteps of a method of manufacturing the light-emitting display shown inFIG. 14.

FIG. 16(A) and FIG. 16(B) are sectional views showing a step followingFIGS. 15(A) and 15(B).

FIG. 17(A) and FIG. 17(B) are a sectional views showing a step followingFIGS. 16(A) and (B).

FIG. 18 is a sectional view showing the configuration of alight-emitting display according to a modification example of the thirdembodiment.

FIG. 19(A) to FIG. 19(D) are sectional views showing the configurationof a mask used in a method of manufacturing a light-emitting displayaccording to a modification example of the invention.

FIG. 20 is a sectional view showing the configuration of alight-emitting display according to a modification example of the firstembodiment corresponding to the case where the mask shown in FIG. 19 isused.

FIG. 21 is a sectional view showing the configuration of alight-emitting display according to a modification example of the secondembodiment corresponding to the case where the mask shown in FIG. 19 isused.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

Preferred embodiments of the invention will be described in detail belowreferring to the accompanying drawings.

First Embodiment

FIGS. 1 and 2 show the configuration of a light-emitting display (anorganic EL display 1) according to a first embodiment of the invention,and FIG. 1 shows a plan configuration and FIG. 2 shows a sectionalconfiguration taken along a line II-II of FIG. 1.

The organic EL display 1 has a laminate configuration in which amultilayer film is laminated between a pair of insulating transparentsubstrates 10A and 10B. More specifically, a gate electrode 11, a gateinsulating film 12, a silicon film 13, a stopper insulating film 14 anda wiring layer 15A are laminated from the transparent substrate 10A sideto constitute a thin film transistor Tr. Moreover, a passivationinsulating film 16 and a planarization insulating film 17A are laminatedon the thin film transistor Tr. On the planarization insulating film17A, an organic EL element EL is formed corresponding to a region wherethe thin film transistor Tr is formed.

Each organic EL element EL has a laminate configuration in which a firstelectrode 18A, an organic light-emitting layer 19 and a second electrode20 are laminated in order from the planarization insulating film 17Aside. Among them, the first electrode 18A and the organic light-emittinglayer 19 are separated from other first electrodes 18A and otherlight-emitting layers 19 by an interelectrode insulating film 21 on theplanarization insulating film 17A, and the first electrodes 18A and theorganic light-emitting layers 19 both having a rectangular shape shownin, for example, FIG. 2 are arranged in a matrix form between thetransparent substrates 10A and 10B. On the other hand, the secondelectrode 20 is a common electrode for the organic EL elements EL, andas shown in FIG. 2, the second electrode 20 is uniformly formed betweenthe transparent substrates 10A and 10B.

As shown in FIGS. 1 and 2, an auxiliary wiring 18B is formed in the samelayer as the first electrode 18A in a region corresponding to a regionbetween the thin film transistors Tr, the first electrodes 18A and theorganic light-emitting layers 19. Moreover, in the planarizationinsulating film 17A and the interelectrode insulating film 21, a forwardtapered aperture having a wide top and a narrow bottom is arranged in apart of a region where the auxiliary wiring 18B is formed (refer to FIG.1). Between a bottom part of the aperture and the gate insulating film12, a conductive contact section 15B is formed in the same layer as thewiring layer 15A, and the second electrode 20 and the auxiliary wiring18B are electrically connected to each other on the contact section 15B.

Moreover, a protective film 23 is uniformly formed on the secondelectrode 20, and a sealing resin 17B is uniformly formed between theprotective film 23 and the transparent substrate 10B. By such aconfiguration, the organic EL display 1 emits light emitted from theorganic light-emitting layer 19 eventually from the second electrode 20side (the transparent substrate 10B side), that is, from the top, so theorganic EL display 1 has a so-called top emission type configuration.

The transparent substrates 10A and 10B are made of, for example, aninsulating material such as a glass material or a plastic material.

The thin film transistor Tr is a drive element for driving each organicEL element EL to emit light. In the thin film transistor Tr, the gateelectrode 11 is made of, for example, molybdenum (Mo) or the like.Moreover, the silicon film 13 is a section where a channel region of thethin film transistor Tr is formed, and is configured of, for example, anamorphous silicon film or the like.

The wiring layer 15A forms a gate electrode and a drain electrode of thethin film transistor Tr, and functions as wiring such as a signal line.The wiring layer 15A is made of the same material as that of the contactsection 15B as will be described later. More specifically, for example,the wiring layer 15A is made of, for example, a conductive materialwhich is resistant to surface oxidation and establishes a goodconnection (desirably an ohmic connection) between the wiring layer 15Aand the second electrode 20. Moreover, as will be described later, amaterial showing high etching selectivity with respect to the firstelectrode 18A is preferable. More specifically, for example, titanium(Ti), titanium nitride (TiN), tungsten (W), chromium (Cr), gold (Au),platinum (Pt), copper (Cu), ITO, IZO (Indium Zinc Oxide) and silver(Ag), an alloy including any one of these metal materials as a maincomponent, and the like are cited. Moreover, the wiring layer 15A may beconfigured of a multilayer film having an uppermost layer made of Tisuch as Ti/Al (aluminum), Ti/Al/Ti, Ti/(AlSi alloy), Ti/(AlSiCu alloy),or Ti/(AlCe (cerium) alloy). In addition, the material of the wiringlayer 15 is appropriately selected by the material of the firstelectrode 18A, an etching method or the like.

The passivation insulating film 16 is provided to protect the thin filmtransistor Tr, and is made of, for example, an insulating materialincluding at least one kind selected from the group consisting of SiO₂,SiN and SiON. Moreover, the planarization insulating film 17A isprovided to planarize a layer configuration and then form the organic ELelement EL on the layer configuration, and is made of, for example, aninsulating material such as a photosensitive polyimide resin, apolybenzoxazole resin, a novolac resin, polyhydroxystyrene or an acrylicresin.

The organic light-emitting layer 19 includes a hole transport layer, alight-emitting layer and an electron transport layer (all not shown)which are deposited in order, and is held between the first electrode18A and the second electrode 20. When a predetermined voltage is appliedbetween the first electrode 18A and the second electrode 20, lightemission is obtained by carrier recombination of electrons and holesinjected into the light-emitting layer.

The first electrode 18A functions as an electrode (an anode electrode ora cathode electrode) for applying a voltage to the organiclight-emitting layer 19 as well as a reflecting electrode for reflectinglight from the organic light-emitting layer 19 to direct the lightupward. Therefore, the first electrode 18A is made of a metal with highreflectivity, for example, Al, an alloy including Al as a main componentsuch as an AlNd (neodymium) alloy or an AlCe alloy. In addition, such amaterial of the first electrode 18A has a property that its surface iseasily oxidized (a surface oxidation property).

The second electrode 20 is also an electrode (an anode electrode or acathode electrode) for applying a voltage to the organic light-emittinglayer 19. The second electrode 20 allows light from the organiclight-emitting layer 19 to pass therethrough, and then emits the lightupward, so the second electrode 20 is a transparent or semi-transparentelectrode. Therefore, the second electrode 20 is made of, for example,ITO or IZO which is a transparent material or a Mg (magnesium)-Ag alloy,Cu, Ag, Mg, Al or the like which is a semi-transparent material.

The auxiliary wiring 18B is formed in a region corresponding to a regionbetween the thin film transistors Tr, the first electrodes 18A and theorganic light-emitting layers 19 as described above, and is provided toprevent in-plane nonuniformity of an electrode voltage in the permeablesecond electrode 20 with high resistance. Therefore, the auxiliarywiring 18B is configured to have lower resistance than the secondelectrode 20 (for example, is made of a material with low resistivity),and more specifically, the auxiliary wiring 18B is made of the samematerial as the above-described material of the first electrode 18A.

For example, as shown in FIG. 1, the contact section 15B is provided toestablish a partial electrical connection between the second electrode20 and the auxiliary wiring 18B, and as described above, the contactsection 15B is formed of the same material as that of the wiring layer15A in the same layer as the wiring layer 15A. In other words, thecontact section 15B is desirably made of a conductive material which isresistant to surface oxidization and establishes a good connection(desirably an ohmic connection) between the contact section 15B and thesecond electrode 20, more specifically a material showing high etchingselectivity with respect to the first electrode 18A. In addition, thematerial showing high etching selectivity with respect to the firstelectrode 18A is used, because although the detail will be describedlater, at the time of forming the first electrode 18A and the auxiliarywiring 18B by etching, the contact section 15B is prevented from beingetched together.

The interelectrode insulating film 21 is provided to separate theorganic EL elements EL from one another, and has a side surface with aforward tapered shape having a wide top and a narrow bottom. In thiscase, the forward tapered shape preferably has as gentle a tilt angle aspossible. Moreover, the width of an aperture in the interelectrodeinsulating film 21 is larger than that of the aperture in theplanarization insulating film 17A in which the contact section 15B isformed, and as shown in FIG. 2, the second electrode 20 has a step-likeshape having a wide top and a narrow bottom in these aperture portions.Thus, the forward tapered shape has as gentle a tilt angle as possibleor the aperture portions are formed in a step-like shape to prevent abreak or an increase in resistance at the time of forming the secondelectrode 20, although the detail will be described later. In addition,the interelectrode insulating film 21 is made of, for example, aninsulating material such as photosensitive polyimide resin.

The protective film 23 is provided to protect the second electrode 20,and is made of, for example, an insulating material including at leastone kind selected from the group consisting of SiO₂, SiN and SiON.Moreover, the sealing resin 17B is provided to planarize a layerconfiguration and then cover the layer configuration with thetransparent substrate 10B.

Here, the thin film transistor Tr corresponds to a specific example of“a drive element” in the invention, and the organic light-emitting layer19 corresponds to a specific example of “a light emission section” inthe invention. Moreover, the planarization insulating film 17A and theinterelectrode insulating film 21 correspond to specific examples of “aninsulating layer” in the invention.

Next, a method of manufacturing the organic EL display 1 will bedescribed below referring to FIGS. 3A to 5B. FIGS. 3A to 5B showsectional views of a part of steps of manufacturing the organic ELdisplay 1.

At first, as shown in FIG. 3(A), the gate electrode 11, the gateinsulating film 12, the silicon film 13, the stopper insulating film 14and the wiring layer 15A which are made of the above-described materialsare laminated in this order on the transparent substrate 10A made of theabove-described material by, for example, a sputtering (chemical vapordeposition) method and a photolithography method to form each of aplurality of thin film transistors Tr in, for example, a matrix form onthe transparent substrate 10A.

In this case, when the wiring layer 15A is formed by, for example, asputtering method, the contact section 15B is also formed of the samematerial as that of the wiring layer 15A in a part of a regioncorresponding to a region between the thin film transistors Tr as shownin FIG. 1 on the gate insulating film 12, that is, in the same layer asthe wiring layer 15A. The material of the wiring layer 15A and thecontact section 15B is appropriately selected by a method of etching ametal layer 18 which will be described later, and, for example, as willbe described later, in the case where wet etching is performed by usinga mixed acid of a phosphoric acid, a nitric acid and an acetic acid, thewiring layer 15A and the contact section 15B can be configured of amultilayer film of Ti/Al/Ti, and the film thickness of the multilayerfilm in this case is, for example, approximately Ti/Al/Ti=50 nm/500nm/50 nm. In addition, in the case of the multilayer film of Ti/Al/Ti,an etching method by RIE (Reactive Ion Etching) is considered; however,in this case, a pattern defect easily occurs, so the etching method byRIE is not preferable.

Next, also as shown in FIG. 3(A), the passivation insulating film 16made of the above-described material is uniformly formed on the thinfilm transistors Tr and the contact section 15B by, for example, a CVDmethod.

Next, referring to FIG. 3(B), the planarization insulating film 17A madeof the above-described material is uniformly formed on the passivationinsulating film 16 by coating by, for example, a spin coat method or aslit coat method. Then, a region corresponding to each contact section15B is exposed and developed by, for example, a photolithography methodto form an aperture, and then firing is performed to form an aperturehaving a side surface with a forward tapered shape shown in a referencenumeral P1 in the drawing. At this time, as a photosensitive resin usedas the planarization insulating film 17A, such a photosensitive resinthat the tilt angle of the aperture becomes as gentle as possible isappropriately selected. To make the tilt angle gentler, the aperture maybe formed through the use of a halftone mask, or an exposure process maybe performed a plurality of times through the use of a plurality ofmasks having different sizes of aperture portions. In addition, the tiltangle of the forward tapered shape is appropriately set by the filmthickness or the forming method of the second electrode 20 which isformed in a later step.

Next, as shown in FIG. 4(A), the metal layer 18 with a thickness of, forexample, approximately 300 nm is uniformly formed of the above-describedmaterial of the first electrodes 18A and the auxiliary wiring 18B (inthis example, a metal material) on the planarization insulating film 17Aand the contact section 15B by, for example, a sputtering method.

Next, as shown in FIG. 4(B), the metal layer 18 is selectively etchedby, for example, a photolithography method to form the first electrodes18A and the auxiliary wiring 18B which have the shapes shown in FIGS. 1and 2. At this time, each first electrode 18A is formed in a positioncorresponding to each thin film transistor Tr, and the auxiliary wiring18B is formed in a region corresponding to a region between the thinfilm transistors Tr. Moreover, patterning is performed so that a part ofthe auxiliary wiring 18B is electrically connected to the contactsection 15B. In this case, as described above, the contact section 15Bis made of a material with high etching selectivity with respect to themetal layer 18, so when the metal layer 18 is etched, there is nopossibility that the contact section 15B is etched together with themetal layer 18. In addition, etching at this time is performed by wetetching using, for example, a mixed acid including a phosphoric acid, anitric acid and an acetic acid.

Next, as shown in FIG. 5(A), the interelectrode insulating film 21 madeof the above-described material is uniformly formed on the planarizationinsulating film 17A, the first electrodes 18A and the auxiliary wiring18B by coating by, for example, a spin coat method or a slit coatmethod, and patterning is performed on the interelectrode insulatingfilm 21 by, for example, a photolithography method so that apredetermined shape is formed, that is, each first electrode 18A andeach organic light-emitting layer 19 which is formed in a later step areseparated from other first electrodes 18A and other organiclight-emitting layers 19. Moreover, at this time, as shown by areference numeral P2 in the drawing, a region corresponding to thecontact section 15B is selectively removed by, for example, aphotolithography method to form an aperture having a side surface with aforward tapered shape. To make the tilt angle as gentle as possible inthe same manner, the aperture may be formed through the use of ahalftone mask, or an exposure process may be performed a plurality oftimes through the use of a plurality of masks having different sizes ofaperture portions. Further, the width of the aperture in theinterelectrode insulating films 21 is configured to be larger than thatof the aperture in the planarization insulating film 17A, and the sidesurface of the aperture portion is formed in a step-like shape.

Next, as shown in FIG. 5(B), the organic light-emitting layer 19 isformed on each first electrode 18A by, for example, a vacuum depositionmethod. Then, the second electrode 20 made of the above-describedmaterial with a thickness of, for example, approximately 10 nm isuniformly formed on the organic light-emitting layer 19, theinterelectrode insulating film 21, the planarization insulating film17A, the contact section 15B and the auxiliary wiring 18B by, forexample, a vacuum deposition method.

Finally, the protective film 23 made of the above-described material isuniformly formed on the second electrode 20 by, for example, a CVDmethod, and the sealing resin 17B is uniformly formed on the protectivefilm 23 by, for example, an instillation method, and is covered with thetransparent substrate 10B made of the above-described material, therebythe organic EL display 1 according to the embodiment shown in FIGS. 1and 2 is manufactured.

In the organic EL display 1, when a voltage is applied to the firstelectrode 18A through the wiring layer 15A and the thin film transistorTr, the organic light-emitting layer 19 emits light with luminanceaccording to a potential difference between the first electrode 18A andthe second electrode 20. The light from the organic light-emitting layer19 is reflected by the first electrode 18A and passes through the secondelectrode, thereby the light is emitted upward, that is, to thetransparent substrate 10B side in FIG. 2. Then, light on the basis of apixel signal is emitted from the organic EL element EL arranged in eachpixel to display a predetermined image on the organic EL display 1.

In this case, in the organic EL display 1, the second electrode 20 andthe auxiliary wiring 18B are electrically connected to each otherthrough the conductive contact section 15B which is resistant to surfaceoxidization and establishes a good connection (desirably an ohmicconnection) between the contact section 15B and the second electrode 20,so even if the surface of the auxiliary wiring 18B made of the samematerial as that of the first electrode 18A is oxidized, an increase inconnection resistance between the second electrode 20 and the auxiliarywiring 18B is prevented.

On the other hand, for example, in a conventional organic EL display 101(a comparative example 1) shown in FIG. 6, an auxiliary wiring 118B isformed of the same material as that of a first electrode 118A in thesame layer as the first electrode 118A, and is directly connected to asecond electrode 120, so when the surface of the auxiliary wiring 118Bis oxidized, connection resistance between the second electrode 120 andthe auxiliary wiring 118B is increased.

Therefore, for example, as shown in FIG. 7, in the comparative example 1shown by a reference numeral G101, in an actually used region of thethin film transistor Tr (a region having approximately a drain currentId=μA to 10 μA), a voltage drop of approximately 1 V occurs due to anincrease in the above-described connection resistance, but on the otherhand, in the embodiment shown by a reference numeral G1, in the sameactually used region, only a voltage drop of approximately 10 μV to 100μV occurs, and as a result, compared to the comparative example 1, thepower consumption of the whole organic EL display is largely reduced.

Moreover, for example, as shown in FIG. 8, in another conventionalorganic EL display 201 (a comparative example 2), an auxiliary wiring218B is formed of the same material as that of the wiring layer 15A inthe same layer as the wiring layer 15A, so an issue of theabove-described increase in connection resistance is prevented; however,it is difficult to form the auxiliary wiring 218B due to a restrictionon layout imposed by the thin film transistor Tr or the wiring layer15A. Moreover, even if the auxiliary wiring 218B can be formed, adistance between wirings is very short, so a short circuit betweenwirings through the auxiliary wiring 218B easily occurs, and the yieldof the display declines.

On the other hand, in the organic EL display 1 according to theembodiment, the auxiliary wiring 18B is formed in the same layer as thefirst electrode 18A, and only a part of the auxiliary wiring 18Bpositioned in a region corresponding to a region between the firstelectrodes 18A is connected to the contact section 15B in the same layeras the wiring layer 15A, so when the contact section 15B is formed,there is no possibility that a restriction on layout is imposed by thethin film transistor Tr or the wiring layer 15A.

As described above, in the embodiment, the second electrode 20 and theauxiliary wiring 18B are electrically connected to each other throughthe conductive contact section 15B, and only a part of the auxiliarywiring 18B is connected to the contact section 15B, so even if thesurface of the auxiliary wiring 18B is oxidized, an increase inconnection resistance can be prevented, and a restriction on layout isnot imposed at the time of forming the contact section 15B. Therefore,while the degree of freedom on layout and low power consumption aremaintained, the display quality of the organic EL display can beimproved.

Moreover, a restriction on layout is not imposed at the time of formingthe contact section 15B, so a short circuit between the contact section15B and the wiring layer 15A due to an unreasonable layout does notoccur, and compared to the conventional organic EL display,manufacturing yields can be improved.

Moreover, the contact section 15B is formed of the same material as thatof the wiring layer 15A in the same layer as the wiring layer 15A, somanufacturing steps are not increased by the formation of the contactsection 15B, and a manufacturing cost can be maintained. In other words,the wiring layer 15A and the contact section 15B can be formed in thesame step, so compared to a second embodiment which will be describedlater, the manufacturing steps can be simplified.

Further, the contact section 15B is formed of a material with highetching selectivity with respect to the first electrode 18A, so when themetal layer 18 is etched to form the first electrode 18A and theauxiliary wiring 18B, there is no possibility that the contact section15B is etched together with the metal layer 18. Therefore, theabove-described contact section 15B can be reliably formed.

Moreover, the side surfaces of the apertures in the planarizationinsulating film 17A and the interelectrode insulating film 21 each havea forward tapered shape having a wide top and a narrow bottom, and thewidth of the aperture in the interelectrode insulating film 21 is largerthan the width of the aperture in the planarization insulating film 17A,so a break or an increase in resistance in the second electrode 20 inside surface portions of the apertures can be prevented, and a declinein manufacturing yields due to this can be prevented.

Second Embodiment

Next, a light-emitting display according to a second embodiment of theinvention will be described below. In addition, like components aredenoted by like numerals as of the first embodiment and will not befurther described.

FIG. 9 shows a sectional configuration of the light-emitting display (anorganic EL display 2) according to the embodiment. In the organic ELdisplay 2, a contact section 22A is formed in the same layer as thefirst electrode 18A and an auxiliary wiring 18C instead of the samelayer as the wiring layer 15A. However, the contact section 22A is madeof a different material from the materials of the first electrode 18Aand the auxiliary wiring 18C. More specifically, as the contact section22A, such a material that its selectivity is increased at the time ofetching the first electrode 18A and the auxiliary wiring 18C is used.Then, as in the case of the first embodiment, the second electrode 20and the auxiliary wiring 18C are connected to each other through thecontact section 22A. In addition, the configurations of other componentsare the same as those in the organic EL display 1 described in the firstembodiment.

Next, a method of manufacturing the organic EL display 2 will bedescribed below referring to FIGS. 10(A) to 13(B). FIGS. 10(A) to 13(B)show sectional views of a part of steps of manufacturing the organic ELdisplay 2.

At first, as shown in FIG. 10(A), the thin film transistors Tr areformed on the transparent substrate 10A as in the case of the firstembodiment, and the passivation insulating film 16 is uniformly formedon the thin film transistors Tr. However, unlike the first embodiment,the contact section 22A is not formed in the same layer as the wiringlayer 15A.

Next, as shown in FIG. 10(B), as in the case of the first embodiment,the planarization insulating film 17A is uniformly formed on thepassivation insulating film 16.

Next, as shown in FIG. 11(A), a metal layer 22 for forming the contactsection 22A is uniformly formed with a thickness of, for example,approximately 50 nm by, for example, a sputtering method. Then, as shownin FIG. 11(B), the metal layer 22 is selectively etched by, for example,a photolithography method to form the contact section 22A in a part of aregion corresponding to a region between the thin film transistors Tr asin the case of the first embodiment.

Next, as shown in FIG. 12(A), the metal layer 22 for forming the firstelectrode 18A and the auxiliary wiring 18C is uniformly formed on thecontact section 22A and the planarization insulating film 17A as in thecase of the first embodiment. Then, as shown in FIG. 12(B), the metallayer 22 is selectively etched by, for example, a photolithographymethod to form each first electrode 18A corresponding to a region whereeach thin film transistor Tr is formed, and to form the auxiliary wiring18C so as to be partially electrically connected to the contact section22A in a region corresponding to a region between the thin filmtransistors Tr. In addition, also at the time of etching the metal layer22, as in the case of the first embodiment, the contact section 22A ismade of a material with high etching selectivity with respect to themetal layer 22, so there is no possibility that the contact section 22Ais etched together with the metal layer 22.

Next, as shown in FIG. 13(A), as in the case of the first embodiment,the interelectrode insulating film 21 is formed in a predetermined shapeon the planarization insulating film 17A, the first electrodes 18A, theauxiliary wiring 18C and the contact section 22A, that is, theinterelectrode insulating film 21 is formed so that each first electrode18A and each organic light-emitting layer 19 which is formed in a laterstep are separated from other first electrodes 18A and other organiclight-emitting layers 19. Moreover, at this time, as shown by areference numeral P3 in the drawing, a region corresponding to thecontact section 22A is selectively removed by, for example, aphotolithography method to form an aperture having a side surface with aforward tapered shape. Then, as in the case of the first embodiment, theaperture is formed through the use of a halftone mask, or an exposureprocess is performed a plurality of times through the use of a pluralityof masks having different sizes of aperture portions so that the tiltangle of the aperture becomes as gentle as possible.

Next, as shown in FIG. 13(B), after each organic light-emitting layer 19is formed on each first electrode 18A as in the case of the firstembodiment, the second electrode 20 is uniformly formed on the organiclight-emitting layers 19, the interelectrode insulating film 21, theplanarization insulating film 17A and the contact section 22A as in thecase of the first embodiment. At this time, as in the case of the firstembodiment, the thickness of the second electrode 20 is adjusted inconsideration of the tilt angle of the forward tapered shape of theaperture in the interelectrode insulating film 21 so as not to cause abreak in the second electrode 20 or an increase in resistance in a tiltportion of the aperture.

Then, finally, the protective film 23 and the sealing resin 17B areuniformly formed in this order on the second electrode 20, and they arecovered with the transparent substrate 10B, thereby the organic ELdisplay 2 according to the embodiment shown in FIG. 9 is manufactured.

As described above, also in the embodiment, the second electrode 20 andthe auxiliary wiring 18C are connected to each other through theconductive contact section 22A, and only a part of the auxiliary wiring18C is connected to the contact section 22A, so the same functions andeffects as those in the first embodiment are obtained. In other words,even if the surface of the auxiliary wiring 18C is oxidized, an increasein connection resistance can be prevented, and a restriction on layoutis not imposed at the time of forming the contact section 22A, so whilethe degree of freedom on layout and lower power consumption aremaintained, the display quality of the organic EL display can beimproved.

Third Embodiment

Next, a light-emitting display according to a third embodiment of theinvention will be described below. In addition, like components aredenoted by like numerals as of the first and second embodiments and willnot be further described.

FIG. 14 shows a sectional configuration of the light-emitting display(an organic EL display 3) according to the embodiment. In the organic ELdisplay 3, the wiring layer 15A and the contact section 15B are amultilayer film in which layers 15A1, 15A2 and 15A3 are laminated inorder from the transparent substrate 10A side and a multilayer film inwhich layers 15B1, 15B2 and 15B3 are laminated in order from thetransparent substrate 10A side, respectively. At least an uppermostlayer (for example, the layer 15A3 or 15A2 or the layer 15B3 or 15B2) ofeach of the multilayer films is made of such a material (for example, Moor Al) that its selectivity is reduced at the time of etching the firstelectrode 18A and the auxiliary wiring 18B (low etching selectivity withrespect to the first electrode 18A or the like is shown), and a lowerlayer (for example, the layer 15A2 or 15A1 or the layer 15B2 or 15B1)than the layer made of such a material showing low etching selectivityis made of such a material (for example, Ti) that its selectivity isincreased at the time of etching the first electrode 18A and theauxiliary wiring 18B (high etching selectivity with respect to the firstelectrode 18A or the like is shown). More specifically, the multilayerfilms are configured of, for example, Mo/Al/Ti in order of the layers15A3, 15A2 and 15A1 and the layers 15B3, 15B2 and 15B1. Thereby, as willbe described later, a part of an upper layer (in this case, the layers15B3 and 15B2) of the contact section 15B is selectively removed at thetime of etching the first electrode 18A and the auxiliary wiring 18B.Moreover, in the organic EL display 3, as shown by a reference numeralP41 in the drawing, the aperture of the interelectrode insulating film21 is formed inside of the aperture of the planarization insulating film17A. In addition, configurations of other components are the same asthose in the organic EL display 1 described in the first embodiment, andthe second electrode 20 and the auxiliary wiring 18B are connected toeach other through the contact section 15B.

Next, a method of manufacturing the organic EL display 3 will bedescribed below referring to FIGS. 15(A) to 17(B). FIGS. 15(A) to 17(B)show sectional views of a part of steps of manufacturing the organic ELdisplay 3.

At first, as shown in FIG. 15(A), as in the case of the firstembodiment, the gate electrode 11, the gate insulating film 12, thesilicon film 13, the stopper insulating film 14 and the wiring layer 15Aare laminated in this order on the transparent substrate 10A to formeach of a plurality of thin film transistors Tr in, for example, amatrix form on the transparent substrate 10A. Moreover, when the wiringlayer 15A is formed, as in the case of the first embodiment, the samematerial as that of the wiring layer 15A is used to form the contactsection 15B together with the wiring layer 15A. However, in theembodiment, as described above, the wiring layer 15A and the contactsection 15B are configured of a multilayer film including the layers15A1 to 15A3 and a multilayer film including the layers 15B1 to 15B3,respectively. More specifically, in the case where the metal layer 18which will be described later is etched by a combination of RIE and wetetching, for example, a multilayer film of Mo/Al/Ti can be formed, andthe film thickness in this case is, for example, approximatelyMo/Al/Ti=50 nm/500 nm/50 nm. In addition, as in the case of the firstembodiment, the passivation insulating film 16 is uniformly formed onthe thin film transistors Tr and the contact section 15B.

Next, as shown in FIG. 15(B), as in the case of the first embodiment,the planarization insulating film 17A is uniformly formed on thepassivation insulating film 16. Then, as in the case of the firstembodiment, an aperture having a side surface with a forward taperedshape shown by a reference numeral P5 in the drawing is formed in aregion corresponding to the contact section 15B.

Next, as shown in FIG. 16(A), as in the case of the first embodiment,the metal layer 18 is uniformly formed through the use of the materialof the first electrode 18A and the auxiliary wiring 18B on theplanarization insulating film 17A and the contact section 15B.

Next, as shown in FIG. 16(B), to selectively etch the metal layer 18 by,for example, a photolithography method, a photoresist film 24 having aselective pattern shown in the drawing is formed on the metal layer 18.Then, when the metal layer 18 is etched by, for example, a combinationof RIE and wet etching as described above, the first electrode 18A andthe auxiliary wiring 18B which have, for example, shapes shown in FIG.17(A) are formed, respectively. In this case, the layers 15B3 and 15B2as an upper layer portion of the contact section 15B are made of amaterial with low etching selectivity with respect to the metal layer 18as described above, so at the time of etching the metal layer 18, a partof the layers 15B3 and 15B2 (more specifically, a portion where thephotoresist film 24 is not formed) is etched together with the metallayer 18. On the other hand, the layer 15B1 as a lower layer portion ofthe contact section 15B is made of a material with high etchingselectivity with respect to the metal layer 18 as described above, so atthe time of etching the metal layer 18, the layer 15B1 is not etchedtogether with the metal layer 18. In addition, at the time of etching,as shown by a reference numeral P6 in the drawing, side etching alsooccurs.

Next, as shown in FIG. 17(B), as in the case of the first embodiment,the interelectrode insulating film 21 is uniformly formed on theplanarization insulating film 17A, the first electrodes 18A and theauxiliary wiring 18B, and patterning is performed on the interelectrodeinsulating film 21 so that each first electrode 18A and each organiclight-emitting layer 19 which is formed in a later step are separatedfrom other first electrodes 18A and other organic light-emitting layers19. At this time, as in the case of the first embodiment, a regioncorresponding to the contact section 15B is selectively removed to forman aperture having a side surface with a forward tapered shape. However,in the embodiment, side etching shown by the reference numeral P6 inFIG. 17(A) occurs, so to prevent a break or an increase in resistance inthe second electrode 20 which is formed in a later step, as shown by areference numeral P7 in FIG. 17(B), the aperture in the interelectrodeinsulating film 21 is formed inside of the aperture of the planarizationinsulating film 17A.

After that, as in the case of the first embodiment, the organiclight-emitting layer 19 is formed on each first electrode 18A, and thesecond electrode 20 is uniformly formed on the organic light-emittinglayer 19, the interelectrode insulating film 21, the planarizationinsulating film 17A, the contact section 15B and the auxiliary wiring18B. Then, the protective film 23 is uniformly formed on the secondelectrode 20, and the sealing resin 17B is uniformly formed on theprotective film 23, and the sealing resin 17B is covered by thetransparent substrate 10B, thereby the organic EL display 3 according tothe embodiment shown in FIG. 14 is manufactured.

As described above, also in the embodiment, the second electrode 20 andthe auxiliary wiring 18B are connected to each other through theconductive contact section 15B, and only a part of the auxiliary wiring18B is connected to the contact section 15B, so the same functions andeffects as those in the first embodiment are obtained. In other words,even if the surface of the auxiliary wiring 18B is oxidized, an increasein connection resistance can be prevented, and a restriction on layoutis not imposed at the time of forming the contact section 15B, so whilethe degree of freedom on layout and low power consumption aremaintained, the display quality of the organic EL display can beimproved.

Moreover, the wiring layer 15A and the contact section 15B each areconfigured of multilayer films (the layers 15A1 to 15A3 and the layers15B1 to 15B3), and at least an uppermost layer of each of the multilayerfilms is made of a material showing low etching selectivity with respectto the first electrode 18A or the like, and a lower layer than the layermade of such a material showing low etching selectivity is made of amaterial showing high etching selectivity with respect to the firstelectrode 18A or the like, so a part of an upper layer (in the case ofFIG. 14, the layers 15B3 and 15B2) of the contact section 15B isselectively removed at the time of etching the first electrode 18A andthe auxiliary wiring 18B; however, there is no possibility that a lowerlayer (in the case of FIG. 14, the layer 15B1) of the contact section15B is selectively removed at the time of etching the first electrode18A and the auxiliary wiring 18B. Therefore, when the wiring layer 15Aand the contact section 15B are configured of multilayer films, somelayers of the multilayer film can be made of a material showing lowetching selectivity with respect to the first electrode 18A or the like,and compared to the first embodiment, the range of choices for thematerial of the wiring layer 15A or the contact section 15B can beexpanded. Therefore, for example, at the time of etching the firstelectrode 18A and the auxiliary wiring 18B, a material which isresistant to an etching defect occurring at the time of etching can bechosen, and in this case, yields can be improved.

Moreover, the side surfaces of the apertures in the planarizationinsulating film 17A and the interelectrode insulating film 21 each havea forward tapered shape with a wide top and a narrow bottom, and theaperture of the interelectrode insulating film 21 is formed inside ofthe aperture of the planarization insulating film 17A, so a break or anincrease in resistance in the second electrode 20 caused by side etchingat the time of etching the metal layer 18 can be prevented, and adecline in manufacturing yields due to this can be prevented.

In addition, in the embodiment, the case where like the organic ELdisplay 3 shown in FIG. 14, the wiring layer 15A and the contact section15B each are configured of a multilayer film, and at least an uppermostlayer of the multilayer film is made of a material showing low etchingselectivity with respect to the first electrode 18A or the like, and alower layer than the layer made of the material showing such low etchingselectivity is made of a material showing high etching selectivity withrespect to the first electrode 18A or the like is described; however,for example, like an organic EL display 4 shown in FIG. 18, the wiringlayer 15A and the contact section 15B each may be configured of a singlelayer (for example, the layer 15A3 and the layer 15B3) made of lowetching selectivity with respect to the first electrode 18A or the like,and the thicknesses of the layers 15A3 and 15B3 may be set so that onlyan upper layer portion of the contact section 15B is partially removedat the time of forming the first electrode 18 by patterning (in otherwords, the thicknesses of the layers 15A3 and 15B3 may be set to athickness to an extent to which a part of the contact section 15B is notpenetrated and removed). In the case of such a configuration, the wholewiring layer 15A or the whole contact section 15B can be made of amaterial showing low etching selectivity with respect to the firstelectrode 18A or the like, and compared to the first embodiment, therange of choices of the material of the wiring layer 15A or the contactsection 15B can be expanded. In addition, even in the organic EL display4, as in the case of the organic EL display 3, as shown by a referencenumeral P42 in the drawing, it is preferable that the side surfaces ofthe apertures in the planarization insulating film 17A and theinterelectrode insulating film 21 each have a forward tapered shape witha wide top and a narrow bottom, and the aperture of the interelectrodeinsulating film 21 be formed inside of the aperture of the planarizationinsulating film 17A.

Although the present invention is described referring to the first,second and third embodiments, the invention is not limited to theseembodiments, and can be variously modified.

For example, when the aperture is formed in the planarization insulatingfilm 17A or the interelectrode insulating film 21 described in theabove-described embodiments, for example, as shown in FIGS. 19(A) and19(B), a halftone mask 5 or a gray tone mask 6 having partialtransmission sections 52 and 62 which allow a part of exposure light L21to pass therethrough as exposure light L22 in addition to a portionallowing exposure light L1 to pass therethrough or light-shieldingsections 51 and 61 shielding exposure light L0 may be used. Moreover,for example, as shown in FIGS. 19(C) and 19(D), exposure may beperformed a plurality of times through the use of a plurality of masks(in this example, two masks 7A and 7B) with different areas of portionsallowing exposure light L1 to pass therethrough. In the case of such aconfiguration, for example, like organic EL displays 1A and 2A shown inFIGS. 20 and 21, respectively (which correspond to modification examplesof the organic EL displays 1 and 2 according to the first and secondembodiments, respectively, and modification examples of the organic ELdisplays 3 and 4 according to the third embodiment are not shown, butare the same as in the case of the organic EL display 1A), a sidesurface portion of apertures in the planarization insulating film 17Aand the interelectrode insulating film 21 can be formed in a step-likeshape having more steps as shown by reference numerals P81, P82 and P9in the drawing, thereby the tilt angle can become gentler. Therefore, inaddition to the effects in the above-described embodiments, a break oran increase in resistance in the second electrode 20 can be prevented.

Further, the position where the contact section is formed is not limitedto the position shown in FIGS. 1, 9 or the like described in theabove-described embodiments, that is, the same layer as the wiring layer15A or the same layer as the first electrode 18A and the auxiliarywiring 18B, and the contact section may be formed in another layer.

Moreover, the light-emitting display according to the invention is notlimited to the organic EL display including an organic EL elementdescribed in the above-described embodiments, and is applicable to anyother light-emitting display.

Further, for example, the material, the thickness, the forming method,the forming conditions and the like of each component described in theabove embodiments are not limited to those described above, and eachcomponent may be made of any other material with any other thickness,and the component may be formed by any other forming method under anyother forming conditions.

Moreover, in the above-described embodiments, the configuration of theorganic EL display is specifically described; however, it is notnecessary to include all layers, or any other layer, for example, acolor filter layer on the transparent substrate 10B side may beincluded.

What is claimed is:
 1. A method of manufacturing a light-emittingdisplay comprising the steps of: forming a drive element and a firstwiring layer over a substrate, and electrically connecting the pluralityof drive elements and the wiring layer; forming a first conductive layerover the drive elements and the wiring layer; forming a first electrodecorresponding to the plurality of drive elements, respectively, as wellas an auxiliary wiring layer by patterning the first conductive layer;forming a respective light emission section on each of the firstelectrodes; forming a common second electrode of a material allowinglight from each light emission section to pass therethrough on theplurality of the light emission sections; and forming a conductivecontact layer, and electrically connecting the common second electrodeand the auxiliary wiring layer through the conductive contact layer,wherein, a portion of the common second electrode is in direct contactwith the conductive contact layer, and a portion of the auxiliary wiringlayer is positioned above and in direct contact with the conductivecontact layer.
 2. The method of claim 1, wherein the wiring layer isformed of a material with resistance that is lower than that of thecommon second electrode.
 3. The method of claim 1, wherein one secondconductive layer is formed, and the first wiring layer and theconductive contact layer are formed by patterning the second conductivelayer.
 4. The method of claim 3, wherein the step of electricallyconnecting the common second electrode and the wiring layer includespartially connecting the common second electrode and the wiring layer toeach other through the conductive contact layer.
 5. The method of claim3, wherein: the second conductive layer is made of a multilayer film inwhich a low etching selectivity film made of a material havingrelatively low etching selectivity with respect to the first electrodesand is placed in at least an uppermost layer, and a high etchingselectivity film made of a material having relatively high etchingselectivity with respect to the first electrodes and is placed in alower layer than the low etching selectivity film.
 6. The method ofclaim 5, further comprising the steps of: forming a planarizationinsulating layer having an aperture in a region corresponding to theconductive contact layer between the conductive contact layer and thecommon second electrode; and forming an interelectrode insulating layerhaving an aperture in a region corresponding to the conductive contactlayer, between the planarization insulating layer and the common secondelectrode, wherein, the aperture of the interelectrode insulating layeris formed inside of the aperture of the planarization insulating layer.7. The method of claim 1, wherein: the second conductive layer is formedof a material having relatively low etching selectivity with respect tothe first electrodes, and the thickness of the second conductive layeris such that only an upper layer portion of the conductive contact layeris partially removed at the time of forming the first electrodes bypatterning.
 8. The method of claim 7, further comprising the steps of:forming a planarization insulating layer having an aperture in a regioncorresponding to the conductive contact layer between the conductivecontact layer and the common second electrode; and forming aninterelectrode insulating layer having an aperture in a regioncorresponding to the conductive contact layer between the planarizationinsulating layer and the common second electrode, wherein, the apertureof the interelectrode insulating layer is formed inside of the apertureof the planarization insulating layer.
 9. The method of claim 1, furthercomprising the steps of: forming an insulating layer between theconductive contact layer and the common second electrode; and forming anaperture having a step-like side surface with a wide top and a narrowbottom by selectively removing a region corresponding to the conductivecontact layer in the insulating layer.
 10. The method of claim 9,wherein the aperture having a step-like side surface is formed throughthe use of a halftone mask or a gray tone mask.
 11. The method of claim1, wherein the conductive contact layer is formed of a material showinghigh etching selectivity with respect to the first electrodes.